During the drilling of oil wells, gas wells and the like, tools, rods and other implements used during the drilling operation may occasionally break or otherwise become lost in the hole. Thus, it becomes necessary to retrieve those lost and broken implements. One type of tool commonly used for that purpose is a fishing tool, as it is commonly referred to in the industry.
Various types of fishing tools have been proposed for retrieving lost and broken implements from drilled holes. For example, U.S. Pat. Nos. 1,491,463 and 1,778,968 disclose fishing tools which include one or more gripping blocks slidably positioned within a bore extending through the tool. The gripping blocks have male keys that fit within slots in the side wall of the bore for supporting the gripping blocks in the bore and for guiding the gripping blocks as they slide along the length of the bore. Unfortunately, the bore in those tools opens through one side of the tool so that the rear surface of the gripping block is not suitably supported by the wall of the bore. When an implement to be retrieved is pinched between the gripping block and the inner wall of the bore, the force that is applied to the gripping block is transferred to the male keys on the gripping blocks. If the force is large enough, the male keys may become damaged. As a result, proper operation of the fishing tool may be adversely affected. It would be desirable, therefore, to develop a fishing tool that is not susceptible to the foregoing drawback.
Other fishing tools such as those disclosed in U.S. Pat. Nos. 1,616,024, 1,732,962, 2,067,009 and 2,201,434 have a main body portion that is fabricated from a plurality of parts. For instance, some of those fishing tools include a separate piece that is secured to the inner surface of the bore for defining an inclined surface upon which the gripping block can be slid. Those fishing tools are fabricated from a plurality of parts which contribute to the complexity and cost of the fishing tool. Further, the multi-part construction requires that those tools be continually checked to ensure that all of the parts are properly positioned relative to one another. Moreover, during use, the connections which secure the various parts of the fishing tool to one another may fail. In view of those disadvantages, it is desirable to design a fishing tool that is simple in construction and reliable during operation.
Some fishing tools, such as the one disclosed in U.S. Pat. No. 2,595,008, are designed in such a manner that it is not possible to interchange the gripping blocks that are used for gripping the implement being retrieved. Consequently, those fishing tools are not well suited for retrieving implements of many different sizes. It can be readily seen, therefore, that it would be advantageous to develop a fishing tool that permits gripping blocks to be readily interchanged for facilitating the retrieval of implements covering a wide range of sizes.
There are specific situations in which it is desirable to provide the bottom portion of the fishing tool with a particular configuration. Similarly, it is desirable in certain instances to provide a smaller or larger opening in the bottom of the fishing tool, depending upon the size of the implement being retrieved and the surrounding conditions. Unfortunately, many of the known fishing tools are not designed to accommodate changes of that sort.
Sometimes, the lost implement is wedged, lodged or otherwise stuck in the hole to such an extent that it may not be possible to pull the lost implement out of the hole once it has been grasped by the fishing tool. Thus, there exists a need for a fishing tool that can readily release an implement while the fishing tool is in the hole.
When an implement has become lost in a hole and needs to be retrieved, it is not always possible to determine with exact precision the size (i.e., diameter or width) of the lost implement. That presents a problem in that typical overshot tools are limited with respect to the size of implements that can be retrieved without changing slips. Thus, if it is found that the fishing tool is not capable of retrieving the implement because the implement is too big, the entire drill string must be removed so that the tool can be outfitted with a different slip. It would be very useful, therefore, to have a fishing tool which possesses the capability of retrieving implements of various sizes without the need for changing the catch slip.
In light of the foregoing drawbacks and disadvantages associated with known fishing tools, it is an object of the present invention to provide a fishing tool that is designed to provide sufficient support for the gripping block, thereby helping to prevent the fishing tool from becoming damaged during use.
It is also an object of the present invention to provide a fishing tool having a body that is fabricated as a single piece, unitary member to reduce the complexity of the structure.
It is another object of the present invention to provide a fishing tool that permits the gripping blocks to be readily interchanged with one another so that the fishing tool can be used to retrieve implements (i.e., fish) covering a wide range of sizes.
It is an additional object of the present invention to provide a fishing tool having readily interchangeable guide bushings and guides so that the configuration of the bottom end of the tool can be varied to suit the particular needs of the operator and the particular conditions of the surrounding environment.
It is another object of the present invention to provide a fishing tool that is capable of easily releasing an implement that has been grasped by the fishing tool while the implement is still in the hole.
A still further object of the present invention is to provide a fishing tool that is able to retrieve lost implements covering a range of sizes without interchanging catch slips.
These and other objects are achieved in accordance with the fishing tool of the present invention which includes an elongated, unitary, one piece body having a bore extending from a bottom end thereof towards an oppositely positioned top end. The bore includes a first bore portion having a longitudinal axis that is substantially parallel to and radially offset with respect to the longitudinal axis of the body and a second bore portion having a longitudinal axis that is transverse to the longitudinal axis of the body. The first and second bore portions are concentric with one another at a point adjacent the bottom end of the body. The body has oppositely positioned male keys extending inwardly from an inner surface of the bore. The male keys extend along a substantial portion of the length of the bore and extend substantially parallel to the second bore portion. A catch slip is slidably positioned within the bore that extends through the body. The catch slip has oppositely positioned slots into which fit one of the male keys for guiding the catch slip as it slides along the length of the bore.
According to further aspects of the present invention, the fishing tool includes a removable guide bushing which is keyed to the bottom end of the body. The guide bushing can be retained in place by a removable guide which is removably secured to the bottom end of the body. The guide bushing and the guide can be configured in various manners to suit the requirements of a particular retrieval operation.